Combine teabags and water in a bowl, stir in currants. Stand overnight or until the currants have absorbed most of the liquid. Carefully squeeze out excess liquid from teabags and throw away.

Stir sifted flour and sugar into current mixture. Pour into tin.

Cook in a moderately slow oven (160C/320F) for about an hour or until cooked when tested with a skewer. Serve warm or cold. Best eaten on day of baking.